This K99/R00 proposal is designed to complement and advance my prior research experience. Briefly, my expertise is in the study of the neuronal mechanisms that modulate reproductive function. I have contributed to the characterization of the roles of kisspeptins (encoded by the Kiss1 gene) as regulatory conduits of gonadotropin-releasing hormone (GnRH) release. During my post-doctoral fellowship, I have broadened this research to include the central modulators of kisspeptin release, neurokinin B (NKB) and dynorphin A (Dyn), which are co-expressed with kisspeptin in the arcuate nucleus (ARC). We have proposed a model whereby NKB and Dyn act through recurrent collaterals to shape the pulsatile release of kisspeptin that would ultimately lead to pulses in GnRH release. The overall goal of this research proposal is to understand the physiological function of subpopulations of Kiss1 neurons that regulate the secretion of GnRH and hence reproduction. Kiss1 expressing neurons are found in two discrete nuclei in the hypothalamus, the ARC and anteroventral periventricular nucleus (AVPV), and are direct targets for the negative and positive feedback action of estradiol E2 on GnRH secretion, respectively. Kiss1 expression in these neurons increases at the time of puberty onset and humans and rodents bearing inactivating mutations in this gene or its receptor (Kiss1r) exhibit impuberism and infertility. The objective of this proposal is to use genetic mouse models in combination with viral-dependent gene therapy to dissect the differential role of the ARC and AVPV Kiss1 and NKB neuronal populations in the control of reproduction. We will use genetically engineered mice that express Cre recombinase and GFP under the Kiss1 promoter. Breeding to homozygosity would lead to Kiss1 deficient (but Cre/GFP positive) mice. Using Cre-dependent adeno-associated viral constructs, we aim to reinsert the Kiss1 gene specifically in Kiss1 neurons of the ARC or the AVPV. The specific aims of the project are to: 1) determine the role of Kiss1 neurons in the ARC vs. AVPV in the control of puberty onset in male and female mice; 2) determine the role of Kiss1 neurons in the ARC vs. AVPV in the positive and negative feedback of sex steroids; and 3) determine the role of NKB in the ARC in the control of puberty in male and female mice. The studies outlined in this proposal are designed to advance our fundamental knowledge of reproductive neuroendocrinology, for the development of better strategies to treat reproductive disorders and offer improved methods of contraception. Completion of these studies will provide training in: (a) state-of-the-art geneti and molecular methodologies; (b) addition of a translational component to my research studies through close interaction with clinical investigators; and (c) skills necessary for success as an independent principal investigator. This additional training will aid in my development of a competitive research program and contribute to my establishment as an independent investigator.